Fluid cushion device for ground effect vehicles and the like



June 18, 1968 J. H. BERTIN 3,

FLUID CUSHION DEVICE FOR GROUND EFFECT VEHICLES AND THE LIKE OriginalFiled Jan. 11, 1962 2 Sheets-Sheet 1 Inuenor Tear; Ber/fin CSWE MMW 1%fowneys J. H. BERTIN June 18, 1968 FLUID CUSHION DEVICE FOR GROUNDEFFECT VEHICLES AND THE LIKE 2 Sheets-Sheet 2 Original Filed Jan. 111962 QN mm Imnswo jean Barin United States Patent 3,388,766 FLUIDCUSHION DEVICE FOR GROUND EFFECT VEHICLES AND THE LIKE Jean H. Eertin,Neuilly-sur-Seine, France, assignor to Societe Bertin & 'Cie, Paris,France, a company of France Original application Jan. 11, 1962, Ser. No.165,634, now Patent No. 3,263,764, dated Aug. 2, 1966. Divided and thisapplication Oct. 20, 1965, Ser. No. 498,250 Claims priority, applicationFrance, June 30, 1961,

866,604, Patent 80,047 8 Claims. (Cl. 180-127) This is a divisionalapplication of my co-pending application Ser. No. 165,634 filed Ian. 11,1962, now Patent No. 3,263,764.

The present invention relates to ground effect vehicles or like movablebodies sustained at a small distance from a ground, sea or other surfaceby means of compressed fluid cushions, in a known manner.

One of the objects of the present invention is to reduce to a minimumthe unavoidable leakage of fluid from said cushions and the compressedfluid consumption.

Another object of this invention is to provide fluidcushion deviceswhich will permit the vehicle to negotiate obstacles without damage andwithout unduly increasing its height above the ground.

A further object of this invention is to provide fluidcushion devicesoffering a good resistance to wear and tear, and yet light and cheap.

In accordance with the present invention, the fluidcushion devicecomprises a skirt made of supple, fluidtight, wear and tear resistingmaterial, adapted to be tensioned by internal over-pressure into a shapeof generally conical or cylindro-conical shape having a downwardlytapering cross-section, which automatically gives the flaccid skirt astable shape when internal pressure is exerted and, in addition, theforces of internal pressure exer'ted on the tapering portion will giverise to a vertical component which puts the skirt under stresslongitudinally.

Other objects and advantages of the present invention will appear in thefollowing description with reference't the accompanying drawings inwhich:

FIGURE 1 is a diagrammatic elevation view, partly in section of a groundeffect vehicle.

FIGURE 2 is a corresponding front elevation view.

FIGURE 3 shows in vertical section a wholly frustoconical skirt inaccordance with the present invention.

FIGURE 4 illustrates similarly a cylindro-conical form of skirt.

FIGURES 5 and 6 show two alternative embodiments of such a skirt.

FIGURES 7 and 8 are respectively a side elevation and a plan view of apreferred arrangement of skirts.

FIGURE 9 illustrates a vehicle with varied skirts.

Referring now to FIGURES 1 and 2, there is shown thereon a platform 1with four gaseous cushions, each supplied by three ejectors 3, theinductive nozzles 4 of which branch off the discharge duct of acompressed gas generator 5, for instance a gas-turbine engine.

Each of said gaseous cushions is of the plenum chamber type and confinedwithin a skirt 2 made of supple material and mounted on a supportingframe 7 gimballed by means of two horizontally opposed pivots 8 andsupported by two horizontally opposed pivots 10 solid with the platform1 and set at right angles to the axis of the pivots 8. The pivots 10 arepreferably fixed to the walls of a flotation tank 21 disposed insideeach cushion.

The upper portion of each skirt 2 provides an oscillation joint, anexample being bellows joint 11, whereby the skirt is able to move freelyin all directions and full tightness with minimum friction is ensured.

Through actuating means well known per se, such as the cable and pulleyassembly shown in FIGURE 8 of Parry 2,953,320, a flight control lever 12controls the pivotal motion of the skirts about the two perpendicularaxes containing respectively the pivots 8 and the pivots 10.

The platform is further equipped with a front orientable wheel 13 and arear wheel 14 driven by an engine 17, for providing positive (friction)guidance and propulsion in a manner well known in the motorcycle art.The wheels are linked to the platform 1 by arms 15, 16 provided withsuspension elements 18 and 19 designed to support only 10 to 20% of thetotal weight of the vehicle, the major part of the weight beingsupported by the gaseous cushions. The suspension elements may beadapted to permit stiffness adjustment, as shown for instance in Brueder2,757,376.

Valves 20 enable the compressed gas supplied by the gas generatingengine 5 to be distributed as desired to the various cushions.

After the engine 5 has been started up, the platform 1 rises on its aircushions and may be piloted by movement of the control lever 12 whichorientates the skirts 2. Accelerations obtained thereby, however, mustbe kept to a low value in order to avoid diminishing the liftingefliciency, and such acceleration will therefore be suited totranslational motion and to low speed manoeuvering.

As a part of the weight of the vehicle is supported by the wheels 13,14, the propulsion of said vehicle may be effected by means of the rearwheel and the accelerations and decelerations exceed those attained byaerodynamic means, with yet a good propulsive efficiency. The tandemwheels will in fact ensure good stability when travelling on the ground,even at cruising speeds, if they support 10 to 20% of the weight and ifthe front wheel 13 is steerable as said hereinbefore. The wheels may befitted with tires having treads adapted to ensure good traction with theground.

The effects of the sideway forces due to the wind are thus reduced, andthe corresponding tipping couple may be further counterbalanced bysuitably operating the valves 20 in a differential manner.

FIGURE 3 illustrates, in vertical half-section, a conical skirt 2h. Thewall of the cushion is in this case inclined, and its open lower end isof smaller area than its upper end fixed to the platform 1 at 34, sothat the force of the pressure F, exerted normal to the wall, produces avertical component V tending to stretch the skirt, in addition to thehorizontal component H which maintains the circular planform.

Considering now FIGURE 4, it will be seen that a similar result may beobtained by providing a conical portion 2 j, of regularly taperingcross-section, "at the bottom of a cylindrical portion 2i.

In both cases, the shapes provided thus ensure stability solely by theaction of the internal pressure, and this in turn makes it possible touse thin skirts made of a convenient supple material which isparticularly resistant to wear and yet not particularly elastic.

It may be desirable to raise a skirt which has been thusshape-stabilized, or even to raise one of its edges only. FIGURE 5 showsa raisable skirt together with its associated raising device.

This skirt, provided with a conical lower portion 2k, comprises an upperbellows-type portion 2l. Rigid hoops 35 prevent any increase in diameterof the bellows. The bottom hoop 35k is connected by cables 36,symmetrically disposed in plan view, to hoist gears such as 37 foradjusting the height of the skirt.

Thus the raising of a skirt may be under the control of a detectedobstacle ahead of it, in which case a mechanical or electro-opticalfeeler or sensing system such as disclosed in Fert, United States2,507,001 or Boncompain, United States 2,535,720, is provided to operatethe hoist gear, but of course it will be understood that such controlmay be entrusted to the pilot if desired. The cables 36 may be connectedto a single hoist gear 37 in order to obtain an even raising of theskirt. It is also manifest that the hoist gears 37 may be controlleddifierentially if required. The orientation of the resulting efiluxprovides a means of controlling yawing motion in the platform, and thismethod of control is equivalent to that used with the gimballedcylindrical skirts described hereabove.

FIGURE 6 illustrates another method of adjusting the length of theskirt. The sides of the skirt are formed in part at least by superposedannular air chambers or tubes 38, the extension of which variesaccording as the tubes are inflated or not. A simple inflating device isprovided in the form of a three-way cock 39, whereby each air tube 38'may be connected through a flexible tube 40 to a pipe supplying gasunder pressure, for example to the compressed air pipe 33 upstream ofthe skirt 2, or to exhaust.

As may be seen from FIGURE 6, it is thus possible to provide a skirtwhich has a bottom conical portion and which is controlled pneumaticallythroughout. More specifically, as explained above, the bottom conicalportion gives rise to a downwardly directed component (of. V on FIGURE3) of force which tends to stretch the skirt longitudinally. If the airtubes 38 are all deflated (as illustrated in the case of the lowest onein FIGURE 6), the skirt will be stretched to its maximum length. Theinflation of one or more air tubes 38 causes a corresponding shorteningof the skirt and therefore a corresponding raising of its lower rim, theminimum length and therefore the highest raising being obtained by fullyinflating all the air tubes 38. If this proves to be insufficient, thepurely pneumatical control of the skirt length by means of the air tubes38 may be supplemented by a mechanical control such as by means of ahoist gear 37 as explained with reference to FIGURE 5. In this case, theair tubes 38 will be again deflated to allow full effectiveness of thehoist gear 37.

It is to be noted that in all the embodiments of skirts illustrated inFIGURES 3 to 6, the flaccid skint, when subjected to internaloverpressure, assumes a relatively rigid outline in the shape of ageometrical solid of revolution, i.e. a shape defined by the motion of aline (generatrix) about an axis, this line remaining in contact with acurve (directrix) extending in a plane perpendicular to this axis. Inthe above embodiments, the directrix is a circle centered on thelongitudinal aixs of the skirt, whereas the generatrix is an obliquestraight line in FIGURE 3, a vertical straight line followed by anoblique straight line in FIGURE 4, a zig-zag line followed by an obliquestraight line in FIGURE 5, an undulated line followed by an obliquestraight line in FIGURE 6.

Thus, in every case, this revolution shape has a crosssection whichdecreases toward the outlet or lower open end of the skirt due to theform of the generatrix which is either entirely (FIGURE 3) or at leastpartly (FIGURES 4, 5 and 6) an oblique straight line, this rectilineargen-- eratrix or rectilinear portion of the generatrix generating afrusto-conical shape. In other words, the skirt, when subjected tointernal overpressure, is in the shape of a frustum of a cone from endto end (FIGURE 3) or at least toward its outlet end (FIGURES 4, 5, and6).

With a view to ensuring an even flow and a correct distribution of airor other gas delivered into the skirt, it has been found convenient tofit a special distributor device at the outlet of the feed pipe 33. Sucha distributor device is shown in FIGURE 3 and consists of a plate 33awhich extends across the outlet of the pipe 33 and which depends fromsupports such as 331).

A preferred distributor device is illustrated in FIG- URE 4 and consistsof a ported plate 33c, which is dished in order to better withstand thepressure and which is fixed to the platform along its periphery. By wayof indication, such a ported plate may have 30%, say, of its areaperforated and absorb about 10% of the overpressure exerted by the gasdischarged from the pipe 33. I

The various drawbacks that arise from the discharge, into the capacitybounded by a skirt, of a high speed jet of small cross-section may beavoided by the use of such distributor devices: one of the most seriousdrawbacks is the tendency of the skirt to be entrained by the jet,thereby causing the supple wall to form folds and to flap about and thejet to discharge directly into the open and to impinge violently on theground, which in turn produces an eroding effect on the soil and givesrise to dust clouds and loss of lift when the lower edge of the skirt isdistant from the ground.

Such devices or equivalents thereof may be used with advantage in allthe forms of construction illustrated in the figures on the accompanyingdrawings.

Individual or elmental skirts such :as described above are preferablyprovided in large number and clustered together to increase platformstability, but this in turn implies a large total efllux or leakageperimeter. Therefore, when it is desired to achieve high liftefficiency, an encompassing peripheral skirt may be used in conjunctionwith the clustered elemental skirts. Referring now to FIG- URES 7 and 8,there is illustrated thereon a peripheral skirt 41 which isfrusto-conical to some degree in side elevation and has a circulardual-lobe planform. Such a skirt may be supplied separately, at anadjustable pressure, rather than be only fed with the leakages from theinner elemental skirts 2.

Adjustment of the relative heights of the skirts 2 and 41 allowsselecting for the platform 1 either a high degree of stability (when theskirts 2 are relatively long with reference to the skirt 41), or greatlifting efficiency (when the skirt 41 is relatively long with referenceto the skirts 2).

An improvement which is applicable to platforms with multiple skirtsconsists in imparting diiferent elasticity characteristics to theelemental skirts supporting such platforms. As will be readilyunderstood, the geometrical size of each skirt, namely its height anddiameter, and its volume in particular, together with its stiffness andthe dimensions of its associated supply duct, all affect theinstantaneous rate of leak-age and determine a natural period ofvertical oscillations of the corresponding air cushion. If all theskirts were identical, such vertical oscillations might give rise toresonance phenomena which may detrimentally affect overall platformsustention. On the other hand, if the elemental skirts be givendifferent sizes, as shown in FIGURE 9, then the natural oscillationperiods of the various air cushions will be different and the sustentionwill tend to be aperiodic.

Thus, in vehicles of this type, the lift and guidance functions may befulfilled, either independently or jointly, by several differentelements such as wheels and air cushions. Such vehicles should extendboth the field of application and the capabilities of wheeled vehiclesused heretofore, in particular over widely varying ground surfaces wheredeep mud, snow or sand may be encountered.

Obviously, the number of air cushions, compressed gas generators,ejectors land so on may be modified as required, and it will be wellunderstood by those skilled in the art that various further changes andmodifications may be made in the presently preferred embodiments of theground effect platform herein-before disclosed, within the spirit andscope of the invention as set forth in the appended claims.

What is claimed is:

1. A skirting device to be fitted to ground effect vehicles or likebodies movable along a bearing surface and designed, in operation, forlaterally bounding a fluid cushion formed against said surface, whereinthe improvement comprises, in longitudinal succession, a body portionmade of superposed inflatable tubes, and an end portion made of thin,flaccid, fluidtight material and tapering toward an end orificedesigned, in operation, to move adjacent to and opposite said surface.

2. A movable body of the ground effect type comprising a support framespaced from a bearing surface along which said body is designed to move,and a skirting device fitted to said frame and designed, in operation,for laterally bounding a fluid cushion formed against said surface, saidskirting device comprising, in longitudinal succession, a body portionmad of superposed inflatable tubes, and an end portion made of thin,flaccid, fluidtight material and tapering toward an end orificedesigned, in operation, to move adjacent to and opposite said surface.

3. A movable body of the ground effect type comprising a support framespaced from a surface along which said body is designed to move, and afluid pressuriza'ble skirt fitted to said frame and designed, inoperation, for laterally bounding a fluid cushion formed against saidsurface, said skint being made of thin, flaccid, fluidtight material andending with an orifice designed, in operation, to move adjacent to andopposite said surface, wherein the improvement comprises a tapering endportion for said skirt extending over a substantial fraction of theoverall length measured from said frame to said orifice, offrustoconical revolution shape having an inclined rectilinear generatrixdefined by two points spaced apart from each other a distance wherebysaid points define a straight line of substantial length, and a circularend rim bounding said orifice and forming the smaller base of saidfrustoconical shape.

4. A body as claimed in claim 3, wherein said skirt further comprises abody portion of cylindrical shape connected to said frustoconical endportion at the larger base thereof and extending said end portion awayfrom said orifice thereof, whereby the skirt has a cylindroconicalrevolution shape.

5. A body as claimed in claim 4, wherein said cylindrical body portioncomprises superposed inflatable tubes.

6. A body as claimed in claim 4, wherein said cylindrical body portioncomprises a section in the form of bellows.

7. A body as claimed in claim 3, wherein said skirt further comprises abody portion of frustoconical revolution shape having the same inclinedrectilinear generatrix as said end portion and extending the same awayfrom the orifice thereof, whereby the skirt has a frustoconical shapesubstantially from end to end.

8. A body as claimed in claim 3, comprising a plurality of separate anddistinct fluid-pressurizable skirts fitted to said frame and made ofthin, flaccid, fluidtight material, each of said skirts having atapering end portion of frustoconical revolution shape with an inclinedrectilinear generat-rix and a circular end rim bounding an orifice.

References Cited UNITED STATES PATENTS 2,743,787 5/1956 Seck 7 3,052,4839/1962 Petersen 180-7 3,055,446 9/ 1962 Vaughen 1807 3,082,836 3/1963Billrnan 180-7 3,118,513 1/1964 Cockerell 180--7 3,134,452 5/ 1964Latimer-Needh am 180-7 3,182,739 5/ 1965 Cockerell a 1807 FOREIGNPATENTS 246,358 9/ 1960 Australia. 860,781 2/ 1961 Great Britain.

A. HARRY LEVY, Primary Examiner.

3. A MOVABLE BODY OF THE GROUND EFFECT TYPE COMPRISING A SUPPORT FRAMESPACED FROM A SURFACE ALONG WHICH SAID BODY IS DESIGNED TO MOVE, AND AFLUID PRESSURIZABLE SKIRT FITTED TO SAID FRAME AND DESIGNED, INOPERATION, FOR LATERALLY BOUNDING A FLUID CUSHION FORMED AGAINST SAIDSURFACE, SAID SKIRT BEING MADE OF THIN, FLACCID, FLUIDTIGHT MATERIAL ANDENDING WITH AN ORIFICE DESIGNED, IN OPERATION, TO MOVE ADJACENT TO ANDOPPOSITE SAID SURFACE, WHEREIN THE IMPROVEMENT COMPRISES A TAPERING ENDPORTION FOR SAID SKIRT